Wikipedia:Reference desk/Archives/Science/2014 October 26
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October 26
[edit]Ebola virus hardiness
[edit]How long does the Ebola virus remain infectious outside a living host (bat, human, dog, swine, or other carriers)? Ebola virus disease says that it is highly infectious on the skin of a dead victim, but for how long? The article just says it is infectious on surfaces for "a few hours." How about on things contaminated by fluids from the victim (blood, feces, vomit) on sheets, toilets, clothing, doorhandles? They went through a great effort to remove everything from the apartment of the Dallas victim's family, but if the stuff becomes noninfectious after "a few hours,"why couldn't they have just locked the door for a day or two, rather than destroying all personal belongings, carpets, etc? When sources say the virus is not infectious after so many hours, does that assume it is exposed to fresh and sunshine, while in moist dampness it could persist indefinitely? I know that some bacterial pathogens sporify such as anthrax, and can remain infectious indefinitely. What about viruses? If the infectious potential only persists for "hours" (2, 20, 200?) then why the ritual of cleaning bowling alleys, taking airplanes out of service, and sending in hazmat cleaners to apartments? Is it a legitimate health precaution or "public health theatre"? Edison (talk)
- How much do we know for sure about ebola? The story seems to change daily. It reminds me of the early years of the AIDS panic. ←Baseball Bugs What's up, Doc? carrots→ 14:41, 26 October 2014 (UTC)
- Yes, health officials have an annoying habit of saying "it can't b spread by X", when they really should say "we haven't yet observed it being spread by X". Now, with a disease that's been around and unchanged for thousands of years, those two are pretty much the same. But in a relatively new and rare disease/strain, you can't just assume that a means of transmission is impossible because you haven't observed it yet. StuRat (talk) 16:06, 26 October 2014 (UTC)
- Your first point is completely untrue. I can virtually guarantee you that no scientist/health official has explicitly said "it can't b [sic] spread by X", and will have said "we haven't yet observed it being spread by X". It's the obnoxious media "simplifying" the accurate wording scientists use for consumption by the ignorant soundbite-expecting public. As a scientist who has had their research misrepresented in the media, I feel this is an important point to make. Fgf10 (talk) 19:05, 26 October 2014 (UTC)
- Have to agree with StuRat on this. Saw it myself on TV. An expert said something along the lines that if a victim is not showing signs and symptoms then s/he is not contagious and they can safely carry on with their normal work. There is something called 'theoretical' risk. Here, in the UK, one can only exhume 'known' smallpox victims if one has had a Small Pox vaccination. Likewise, if an archaeologist is exploring a plague pit, then it is understood that there is a 'theoretical' risk of contracting Yersinia pestis. (doctors have a saying: If you hear hoofs... think horses not zebras( the common not the exotic) Meaning: A doctor would not normally consider a patient with a cough as having Yersinia pestis. But if his patient says Oh and by the way, I am an archaeologist and currently working in an old plague pit, the doctor can then switch mode and consider the possibility of plague. This is because medial science does not know exactly how long the causative agents of these two diseases remain viable. The experts on TV where pontificating about thing that they have no scientific evidence for. Yet, perhaps, the allure of appearing on TV, overcame their conservatism and good judgment.--Aspro (talk) 22:50, 26 October 2014 (UTC)
- I haven't heard the statement about Ebola that "It can't be spread by X". I did hear the statement about HIV that "It can't be spread by X", in particular to "It can't be spread by insects", when the Belle Glade cluster of HIV infections still isn't explained unless it was a rare case of the virus being spread by mosquitos. Statements that "it can't be spread by X" are more appropriate to varicella or to Y. pestis, with centuries of data, than to Ebola, and by now HIV is somewhere in between. (I think that it can reasonably be said that Ebola can't be spread by mosquitos, because if it could, most of the population in Liberia, Sierra Leone, and Guinea would be infected, but no one said that it could be spread by mosquitos. That isn't an argument against effective mosquito control, because malaria is still a serious problem in those countries.) Robert McClenon (talk) 15:59, 27 October 2014 (UTC)
- Have to agree with StuRat on this. Saw it myself on TV. An expert said something along the lines that if a victim is not showing signs and symptoms then s/he is not contagious and they can safely carry on with their normal work. There is something called 'theoretical' risk. Here, in the UK, one can only exhume 'known' smallpox victims if one has had a Small Pox vaccination. Likewise, if an archaeologist is exploring a plague pit, then it is understood that there is a 'theoretical' risk of contracting Yersinia pestis. (doctors have a saying: If you hear hoofs... think horses not zebras( the common not the exotic) Meaning: A doctor would not normally consider a patient with a cough as having Yersinia pestis. But if his patient says Oh and by the way, I am an archaeologist and currently working in an old plague pit, the doctor can then switch mode and consider the possibility of plague. This is because medial science does not know exactly how long the causative agents of these two diseases remain viable. The experts on TV where pontificating about thing that they have no scientific evidence for. Yet, perhaps, the allure of appearing on TV, overcame their conservatism and good judgment.--Aspro (talk) 22:50, 26 October 2014 (UTC)
- Your first point is completely untrue. I can virtually guarantee you that no scientist/health official has explicitly said "it can't b [sic] spread by X", and will have said "we haven't yet observed it being spread by X". It's the obnoxious media "simplifying" the accurate wording scientists use for consumption by the ignorant soundbite-expecting public. As a scientist who has had their research misrepresented in the media, I feel this is an important point to make. Fgf10 (talk) 19:05, 26 October 2014 (UTC)
- Yes, health officials have an annoying habit of saying "it can't b spread by X", when they really should say "we haven't yet observed it being spread by X". Now, with a disease that's been around and unchanged for thousands of years, those two are pretty much the same. But in a relatively new and rare disease/strain, you can't just assume that a means of transmission is impossible because you haven't observed it yet. StuRat (talk) 16:06, 26 October 2014 (UTC)
- I had read that the virus can survive for a couple of hours on a hard, dry surface - up to 24 hours on moist/soft surfaces and an unknown, but definitely much larger, amount of time in human corpses. A lot of the caution involved here is because there are unknowns. This virus is just not that well understood - and there is always the possibility of mutant strains that can break the rules. When you're dealing with something with the ability to become an unstoppable global pandemic with a potential for deaths in the billions, an excess of caution is definitely required.
- Viruses are tremendously variable in their capabilities. The HIV virus is incredibly fragile and can hardly exist outside of the human body at all. The classic Tobacco mosaic virus can live for up to nine years on a dessicated plant leaf - and can form essentially inorganic crystals that can survive for decades in a wide range of conditions - it's capable of infecting 120 different plant species in nine distinct families. I'm sure there are examples all along that spectrum.
- SteveBaker (talk) 14:56, 26 October 2014 (UTC)
- This virus was first written up years ago. It clearly is of interest in the public health world, and could potentially cost many lives and many billions of dollars economic disruption. It is surprising if no controlled studies were done to furnish reliable answers to obvious questions such as I posed about how authorities can do the minimum disruption to ensure some contaminated apartment, bathroom, school, cruise ship or shopping mall will not be a source of future cases. Overreaction ("public health theatre") to reassure the public seems to be the rule so far in the U.S if the statements about a few hours or 24 hours for the infection potential of fluid deposits is correct. If some animal species is infected in a similar manner to humans (lab rats, or rabbits ideally, or even swine perhaps?) it would seem straightforward to do parametric testing and determine what measures are really necessary when an infected person has deposited his bodily fluids on something. If semen remains infective for weeks after the accepted 21 days, then what about blood? Ebola survivors are welcomed a a curative to transfuse new victims. This seems to be an anomaly. Edison (talk) 18:21, 26 October 2014 (UTC)
- The main reason is that "this virus" hasn't been seen before. Every strain of Ebola is potentially a whole new surprise - see Ebola Reston for how surprising they can be. Though the reaction to that potential surprise should not have been first to broadly assure people that casual contact won't spread the virus, then to discount abundant fatalities in Liberian health workers as the result of poverty and ignorance, and only to start freaking out and taking protective measures after a couple of Americans die.
- As far as viral stability in general, I think the viral envelope is a consideration. Viruses like HIV and Ebola that have envelopes are actually made up, in part, of a mix of phospholipids from the host's plasma membrane. This means that lipid peroxidation would seem inevitably to be a limitation. (Caveat: there's no literal guarantee that the virus couldn't totally shield itself from oxygen, or work even after the envelope is severely oxidized... I do doubt it though) Without taking time to really dive into the topic I'm only finding possibly-irrelevant references for this though like PMID 18598719, PMID 8686266. Wnt (talk) 13:20, 28 October 2014 (UTC)
- This virus was first written up years ago. It clearly is of interest in the public health world, and could potentially cost many lives and many billions of dollars economic disruption. It is surprising if no controlled studies were done to furnish reliable answers to obvious questions such as I posed about how authorities can do the minimum disruption to ensure some contaminated apartment, bathroom, school, cruise ship or shopping mall will not be a source of future cases. Overreaction ("public health theatre") to reassure the public seems to be the rule so far in the U.S if the statements about a few hours or 24 hours for the infection potential of fluid deposits is correct. If some animal species is infected in a similar manner to humans (lab rats, or rabbits ideally, or even swine perhaps?) it would seem straightforward to do parametric testing and determine what measures are really necessary when an infected person has deposited his bodily fluids on something. If semen remains infective for weeks after the accepted 21 days, then what about blood? Ebola survivors are welcomed a a curative to transfuse new victims. This seems to be an anomaly. Edison (talk) 18:21, 26 October 2014 (UTC)
- Think Wnt is on the right track. 99.9% of the time, clinicians can be assured that each viral infection will follow the same course as the last, but occasionally an un-caricaturist epidemic brakes out, which suggests that a virus strain has mutated. In the fullness of time, maybe will we have a full RNA analysis, so know if this was the case. The point is: when such an un-caricaturist out outbreaks like this occurs, received medical dogma (like we heard at the start of the outbreak) should be replaced with Err , this is unusual. Let's look at this without letting medical dogma cloud our vision. Trouble is, that it appears to me that the individuals that move up from practising healthcare to administrators, loose touch with the reality of diseases. For someone of my age it was only a few decades ago that HIV/AID's was considered to be akin to GPI. Thought to be a psychiatric disorder attributed to the 'immorality of homosexuals'. Then heterosexuals started getting diagnoses with it. By then it had become wide spread and prepubescent children were contracting it from blood transfusions. When the Apollo 11 crew came back, were they not held in quarantine on the precautionary principle? There is only so much money in the pot for healthcare, so shouldn't that money be wisely directed to issues that may pose the greatest threat -by the experts that know , rather than left in the hands of administrators that use political one-upmanship to elevate their status (and financial remunerations)? This is the 21st Century, so let,s have protocols put in place to nip these emerging plagues in the bud. It will be less expensive in the long run.--Aspro (talk) 23:08, 28 October 2014 (UTC)
- A thought has just come to me. Air travel is a lot safer to day than in the past. Much of this is because airline pilots have to undergo 'Recertification' [1]. This ensures that they haven't developed any bad habits, haven't forgotten the basic etc. Ie, still competed to be responsible for several hundred passengers (souls; men, women, children, grandparents etc.). Some of the healthcare representatives that I have seen of late on TV are responsible for the well-being of a hell of a lot more people, (millions). Should they not undergo recertification as well? Human kind has (slowly) progressed, by getting rid of the smooth talking pontificators who play politics for all their worth and replacing them with competent specialists. History has show that this is more economic in the long run.--Aspro (talk) 23:40, 28 October 2014 (UTC)
- To identify oneself as an Infectious Diseases physician in the United States, one has to maintain certification - now a continual process of learning modules, practice improvement modules, and in-person examinations. Many adult Infectious Diseases clinicians also maintain certification in Internal Medicine, which requires continual recertification as well. Of course, some are just "pundits", and anyone with an ego (e.g. George Will on the subject of Ebola virus becoming airborne) can do that. -- Scray (talk) 14:51, 29 October 2014 (UTC)
- Problem with this type of re-certification. It often requires 'only' oneself to keep up to date with how to prescribe patented medications. Not how to alert you, that a disease is no longer conforming to the accepted epidemiological pattern. Nor what to do when a disease shows it doesn't give two hoots about what you-think-you-know about it!--Aspro (talk) 14:50, 30 October 2014 (UTC)
- To identify oneself as an Infectious Diseases physician in the United States, one has to maintain certification - now a continual process of learning modules, practice improvement modules, and in-person examinations. Many adult Infectious Diseases clinicians also maintain certification in Internal Medicine, which requires continual recertification as well. Of course, some are just "pundits", and anyone with an ego (e.g. George Will on the subject of Ebola virus becoming airborne) can do that. -- Scray (talk) 14:51, 29 October 2014 (UTC)
- A thought has just come to me. Air travel is a lot safer to day than in the past. Much of this is because airline pilots have to undergo 'Recertification' [1]. This ensures that they haven't developed any bad habits, haven't forgotten the basic etc. Ie, still competed to be responsible for several hundred passengers (souls; men, women, children, grandparents etc.). Some of the healthcare representatives that I have seen of late on TV are responsible for the well-being of a hell of a lot more people, (millions). Should they not undergo recertification as well? Human kind has (slowly) progressed, by getting rid of the smooth talking pontificators who play politics for all their worth and replacing them with competent specialists. History has show that this is more economic in the long run.--Aspro (talk) 23:40, 28 October 2014 (UTC)
- Think Wnt is on the right track. 99.9% of the time, clinicians can be assured that each viral infection will follow the same course as the last, but occasionally an un-caricaturist epidemic brakes out, which suggests that a virus strain has mutated. In the fullness of time, maybe will we have a full RNA analysis, so know if this was the case. The point is: when such an un-caricaturist out outbreaks like this occurs, received medical dogma (like we heard at the start of the outbreak) should be replaced with Err , this is unusual. Let's look at this without letting medical dogma cloud our vision. Trouble is, that it appears to me that the individuals that move up from practising healthcare to administrators, loose touch with the reality of diseases. For someone of my age it was only a few decades ago that HIV/AID's was considered to be akin to GPI. Thought to be a psychiatric disorder attributed to the 'immorality of homosexuals'. Then heterosexuals started getting diagnoses with it. By then it had become wide spread and prepubescent children were contracting it from blood transfusions. When the Apollo 11 crew came back, were they not held in quarantine on the precautionary principle? There is only so much money in the pot for healthcare, so shouldn't that money be wisely directed to issues that may pose the greatest threat -by the experts that know , rather than left in the hands of administrators that use political one-upmanship to elevate their status (and financial remunerations)? This is the 21st Century, so let,s have protocols put in place to nip these emerging plagues in the bud. It will be less expensive in the long run.--Aspro (talk) 23:08, 28 October 2014 (UTC)
Difference between diffusion of vapors and diffusion of gases
[edit]In today's present, it is been obvious that the separate sections of practical physics of thermodynamics thermostatics already had not been scientific perspectives. However, there is been a fundamental difference between the physical phenomena diffusion of vapors and diffusion of gases, so that, is been any significant technical differences between the steam turbine and gas turbine?--Alex Sazonov (talk) 17:03, 26 October 2014 (UTC)
- There is no difference between a vapour and a gas, those terms are synonyms. However, technically speaking, steam is not a vapour, but an aerosol. That being said, at the macroscopic scale, steam is equivalent to a vapour, albeit constituted of very large "molecules" (droplets). Since the droplets that from the steam are significantly larger than individual molecules in gas, kinetic friction plays a much more important role when discussing wear and tear on a turbine. The design and operation of the steam turbine would need to compensate for the difference. If steam is heated to above 100°C, it becomes an actual vapour - water vapour. I suspect that most "steam" turbines are actually water vapour turbines. Plasmic Physics (talk) 22:20, 26 October 2014 (UTC)
- More precisely, the word "steam" is used in two different ways. Either it means water vapor or it refers to the aerosol mist formed by water vapor condensing in air. In the context of steam locomotives, steam turbines, and so on, it means water vapor. See here or here, for example.--174.88.134.249 (talk) 04:56, 27 October 2014 (UTC)
- The term "steam quality" refers to any of a variety of engineering approximations about the percentage of steam that is gaseous water, compared to the percentage that is suspended droplets of water. Nimur (talk) 22:47, 26 October 2014 (UTC)
- Did the vapour and gases been homogeneous substance and uniformity of aggregate physical states of matter, that could be considered as the same physical phenomenon?--Alex Sazonov (talk) 04:13, 27 October 2014 (UTC)
- Did the dynamical kinetics of vapour and gases been the homogeneous dynamical kinetics?--Alex Sazonov (talk) 11:51, 27 October 2014 (UTC)
- Did the vapour and gases been homogeneous substance and uniformity of aggregate physical states of matter, that could be considered as the same physical phenomenon?--Alex Sazonov (talk) 04:13, 27 October 2014 (UTC)
- Combining advanced terminology with your level of English is probably not the best choice in this instance. I for one, am completely confused by what you are trying to ask. Try asking with simpler words, then we can try to interpret what you mean to ask. Plasmic Physics (talk) 20:35, 27 October 2014 (UTC)
- ... and please don't make your words harder to understand by adding been to every sentence? The present tense (third person) of the English verb "to be" is just "is". Dbfirs 00:01, 28 October 2014 (UTC)
- Now, now, we're not here to fix others' grammar to the nth degree. I'm simply trying to help him, help others to interpret for themselves what he is trying to communicate. Plasmic Physics (talk) 03:21, 28 October 2014 (UTC)
- Despite the fact that the physics of thermodynamics and thermostatics studied so, that they had no scientific perspectives. I'm interested in acceptable and unacceptable methods of studying thermodynamics and thermostatics of homogeneous physical environments and their aggregate physical condition.--Alex Sazonov (talk) 09:31, 28 October 2014 (UTC)
- OK, you're asking about scientific methodology? I don't know if there is particular which is more applicable to the field of thermodynamics than any other field of science, but try scientific method. Plasmic Physics (talk) 05:28, 29 October 2014 (UTC)
- What is a concrete scientific method of studies did concludes about the homogeneous of the physical environment of gases and vapour?--Alex Sazonov (talk) 07:29, 29 October 2014 (UTC)
- OK, you're asking about scientific methodology? I don't know if there is particular which is more applicable to the field of thermodynamics than any other field of science, but try scientific method. Plasmic Physics (talk) 05:28, 29 October 2014 (UTC)
- What is "Homogeneous of the physical environment"? Dynamic equilibrium? Plasmic Physics (talk) 08:34, 29 October 2014 (UTC)
- In what why the diffusion of gases always had become to an explosion of gases and diffusion of vapour always had become to condensation of vapour?--Alex Sazonov (talk) 09:40, 29 October 2014 (UTC)
- What is "Homogeneous of the physical environment"? Dynamic equilibrium? Plasmic Physics (talk) 08:34, 29 October 2014 (UTC)
- My apologies, but I'm abandoning this thread. It is simply too difficult to interpret. Plasmic Physics (talk) 10:09, 29 October 2014 (UTC)
- I’m explain this by the physical fact, that the gases and vapour are always had during none homogeneous thermodynamic and thermostatic processes, that is at the basis of the dynamics of vapour and dynamics of gases as well as their statics are always been a different physical phenomena.--Alex Sazonov (talk) 10:31, 29 October 2014 (UTC)
- Phenomena of physics of gases are always been different from the phenomena of physics of vapour.--Alex Sazonov (talk) 14:02, 29 October 2014 (UTC)
- My apologies, but I'm abandoning this thread. It is simply too difficult to interpret. Plasmic Physics (talk) 10:09, 29 October 2014 (UTC)
- I interpret one question to be whether a turbine optimally designed for a vapor (a gas at less than the critical temperature) would also be optimally designed for use with a supercritical fluid. My suspicion is that supercritical fluids are less compressible and this should affect the design, but I know nothing about turbines! Wnt (talk) 13:36, 28 October 2014 (UTC)